1. Field of the Invention
The present invention relates to an arrangement on packing machines for the cleaning of a filling pipe of the type which has two or more ducts for the supply of contents or gas, this arrangement comprising a pump for the pumping of cleaning fluid and devices for the steering of the fluid flow to the filling pipe.
2. Description of Related Art
Machines for the manufacture of packing containers for fluid contents, e.g., milk, juice, soups or sauces, usually fill the packing containers with the help of a filling pipe when they are in a more or less finished state, e.g., in the form of a coherent tube or of separate packing containers open at the top. The filling pipe here extends with a free end partly down into the packing containers, and the opposite end of the filling pipe is connected via a system of ducts or valves to a product line for the supply of contents from a conventional contents tank. Frequently the filling pipe comprises a number of supply ducts which may be intended for different parts of the contents (e.g. pieces of vegetable and meat via one duct and a liquid part of soup via another duct) or they may be intended for contents and an inert gas respectively, the latter having the object of filling up the so-called head-space in the packing container and preventing contact between the contents and the surrounding atmosphere.
When a machine comprising a filling pipe system of the above-mentioned type is to be washed after completed package production, this is done with the help of a washing or cleaning fluid which is pumped through the filling pipe and the valves connected to the filling pipe so as to remove residues of contents. Generally this is done over a relatively long period of time, and in order to utilize the cleaning fluid in an optimum manner, the same is circulated over a large part of the time in a closed system realized with the help of connecting ducts, which comprises also the filling pipe and product valves connected to the same. The cleaning effect required is achieved only if the cleaning fluid can be circulated at a certain minimum rate. In packing machines intended for the manufacture of packing containers of relatively small size the outer dimensions of the filling pipe are limited for obvious reasons, which means that the area of the supply ducts is relatively small. As a result the flow of cleaning fluid will be reduced, which implies that the cleaning effect is impaired in the parts of the machine connected to the circulation system where the free area is larger, e.g., in the valve body and similar passages. The flow through the said parts can be increased by coupling the ducts of the filling pipe in parallel so that the cleaning fluid passes not only through the contents duct but also, e.g., through the gas duct, even if the same normally is not in contact with the contents and therefore, strictly speaking, does not require to be cleaned. In this way, however, a larger flow through the filling pipe is made possible so that the necessary washing effect can be achieved also with regard to the valve body and other larger passages in the system. However, it is a disadvantage of this so-called parallel-washing that it is not possible to determine from the outside with certainty whether the contents duct is cleaned in a proper manner. This is due to the fact that if, for example, the contents duct is wholly blocked by contents, the cleaning fluid is conducted via the parallel gas duct so that the circulation system appears to function perfectly, in spite of no cleaning fluid at all flowing through the contents duct. Even minor blockages of the contents duct may lead to an impaired washing effect, which means that there is a danger of a loss of production when the machine is to be started again and the manufacture of filled packing containers is commenced.